1. Field of the Invention
The present invention relates to a method of manufacturing a multi-layer wiring board.
2. Description of Relate Art
In general, as a package having electronic components mounted thereon, a multi-layer wiring board has been used in which resin insulating layers and conductor layers are alternately formed on both sides of a core substrate to form buildup layers (JP-A-11-233937). In the multi-layer wiring board the core substrate is made of a resin including, for example, a glass fiber, that has high rigidity and reinforces the buildup layers. However, since the core substrate has a large thickness, it hinders a reduction in the size of the multi-layer wiring board. Therefore, in recent years, the thickness of the core substrate has been reduced to reduce the size of the multi-layer wiring board.
However, when the thickness of the core substrate is reduced, the strength of an assembly including the core substrate is reduced during a manufacturing process and it is difficult to horizontally convey the core substrate or the assembly. During conveyance, the core substrate or the assembly (substrate which is being manufactured and will be the multi-layer wiring board) comes into contact with a conveyance mechanism and is damaged. In addition, the core substrate or the assembly is fixed in each manufacturing process. When the core substrate or the assembly is provided to a predetermined manufacturing process, it is bent, which makes it difficult to perform, for example, a plating process with high accuracy. As a result, in the multi-layer wiring board including the core substrate, when the thickness of the core substrate is reduced, the manufacturing yield of the multi-layer wiring board is reduced.
From this point of view, a so-called coreless multi-layer wiring board has been proposed which does not include a core substrate, is suitable to reduce the size, and is capable of improving the transmission performance of a high-frequency signal (JP-A-2009-289848 and JP-A-2007-214427). For example, the coreless multi-layer wiring board is formed as follows. A buildup layer is formed on a supporting substrate on which a release sheet, which is a laminate of two separable metal films, is formed and the release sheet peels off at the peeling interface between the two metal films to separate the buildup layer from the supporting substrate. In this way, a desired multi-layer wiring board is obtained.
However, since no core layer is provided in the coreless multi-layer wiring board, the strength of the coreless multi-layer wiring board is weak and the coreless multi-layer wiring board requires careful handling. In addition, the purpose of the coreless multi-layer wiring board is limited.